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At least 775 records · Page 43Linked to original sources
PubMed1994

More talk, less paper: predicting the accuracy of substituted judgments.

PURPOSE: To study the accuracy of substituted judgments regarding life-sustaining therapies and other therapies made by surrogate decision makers and to investigate factors associated with more accurate predictions. PATIENTS AND METHODS: A total of 50 pairs of ambulatory patients and surrogates, chosen according to a legal hierarchy, underwent separate interviews in which surrogates were asked to predict the preferences of patients for eight modes of medical therapy in three clinical scenarios, given only yes or no as response options. Patient preferences, their surrogates' predictions, and the extent of agreement between the two were measured. The total number of correct predictions constituted the Surrogate Accuracy in Matching Patient Preferences Scale (SAMPPS). Sociodemographic factors associated with agreement were also assessed. RESULTS: Agreement between patients and surrogates ranged from 57% to 81%. The mean SAMPPS score was 17 of 24 correct. Kappa (k) coefficients, which measure inter-rater concordance, were positive for 23 of 24 items and were 0.3 or greater (P < 0.05) for 14 of 24 items. Rates of agreement were not related to whether the surrogate interviewed (surrogate determined by state law) was the person the patient would have chosen as a surrogate or whether the patient had an advance directive. In multiple linear regression analysis, both prior discussions of preferences and nonchurchgoing behavior were significantly associated with patient-surrogate agreement, independent of religious denomination and race. CONCLUSION: When pressed to choose, surrogates can predict the preferences of patients for life-sustaining therapies with an imperfect accuracy that nonetheless significantly exceeds the agreement expected due to chance alone. Exhorting surrogates to give their "best estimate" and encouraging prior discussions may improve accuracy. Houses of worship might be important target sites for campaigns to improve public awareness about advance directives.

Adult↗
PubMed1984

Accuracy of the hepatobiliary scan in acute cholecystitis.

The accuracy of the hepatobiliary scan in the diagnosis of acute cholecystitis was determined at a major United States Army Medical Center. Forty-two patients with complete medical records were selected for the study. There was 18 positive findings and 24 negative findings. The accuracy rate for the positive findings for acute cholecystitis was 97 percent, whereas the accuracy rate for the negative findings was 100 percent. The accuracy of the hepatobiliary scan was found to be similar to that reported in the literature.

Acute Disease↗
PubMed1984

Comparative analysis of translation accuracy in an Escherichia coli and a mammalian cell-free system.

The effect of environmental stress on the accuracy of protein synthesis in an Escherichia coli and a rat brain cell-free system was investigated. Poly-U was translated in a rat brain and an E. coli cell-free extract under identical ionic conditions. The fidelity of translation, both in the E. coli and the rat brain extracts, was commensurate with what is known about the accuracy of translation in vivo. The incorporation of phenylalanine (code: UUU) and leucine (code: CUU, UUG or A) was measured at various Mg2+ concentrations (3 to 22 mM), various pH's (6.6 to 8.6), various temperatures (23 to 42 degrees C), and in the presence or absence of 2.4% (v/v) ethanol. It was observed that (i) the accuracy of translation was generally higher in extracts from E. coli than from rat brain, and (ii) relative to that in E. coli, the translation fidelity in rat brain extracts was about 2 times more sensitive to ethanol, at least 5 times more sensitive to temperature, and at least 50 times more sensitive to pH. It was found that this differential sensitivity was not due to a differential behavior of the bacterial and the mammalian aminoacyl-tRNA synthetases under stress, but rather to the process of chain elongation itself. It is concluded that the accuracy of protein synthesis is more resistant to environmental stress in E. coli extracts than in extracts from at least one mammalian tissue.

Amino Acyl-tRNA Synthetases↗
PubMed1993

Subsensitivity of lead-exposed rats to the accuracy-impairing and rate-altering effects of MK-801 on a multiple schedule of repeated learning and performance.

Exposure to lead (Pb) has been reported to inhibit MK-801 binding and to alter other NMDA receptor complex-associated functions. These reported changes are provocative since both NMDA receptor antagonism and Pb exposure are know to impair learning processes. Whether the Pb-induced changes in NMDA function relate to the learning impairments associated with Pb exposure, however, has not been explored. The contention of this study was that if changes in NMDA function produced by Pb serve as the basis of Pb-associated learning impairments, then such changes should be of sufficient biological magnitude and clinical relevance to induce alterations in sensitivity at the level of the whole animal, i.e., changes in behavioral sensitivity to glutamatergic compounds. Thus, in this study, dose-effect curves of control and Pb-treated rats working on a multiple schedule of repeated learning (repeated acquisition, RA) and performance (P) were compared following acute administration of MK-801, the non-competitive NMDA antagonist. Based on the nature of the reported effects of Pb on NMDA systems, it was expected that the curves of Pb-exposed rats would be right-shifted relative to controls, if differential behavioral sensitivity was evident. Rats were chronically exposed to 0, 50 or 250 ppm Pb acetate in drinking water from weaning and trained on the multiple RA and P schedule beginning at 55 days old. The RA component required the rat to learn a new 3-member sequence of responses during each experimental session (center right left, RLC, CLR, RCL, or LRC), while the correct sequence of responses for the P component was constant across sessions (LCR), requiring performance of an already learned response. Acute administration of MK-801 (0.05-0.3 mg/k, i.p.) resulted in decrements in accuracy in both the RA and P components of the schedule, indicative of non-specific effects on behavior rather than selective effects on learning. The declines in accuracy during the RA component of the schedule were primarily the result of increased perseverative responding, i.e., repetitive responding on a single lever. Both the decline in RA accuracy and the increases in perseverative responding produced by MK-801 were attenuated by Pb exposure. Moreover, dose-effect curves relating MK-801 dose to changes in rates of responding were significantly shifted to the right in Pb-exposed rats relative to controls. Taken together, these data demonstrate a subsensitivity of Pb-exposed rats to both the accuracy-impairing and response rate-altering properties of MK-801.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

An investigation on the accuracy of three-dimensional space reconstruction using the direct linear transformation technique.

An investigation on the three-dimensional calibration errors associated with the direct linear transformation (DLT) technique was carried out using a two video camera system. Thirty different configurations in five groupings of different numbers of control points were tested. The results showed that the accuracy improved as the number of control points increased from 8 to 24. Further, it was demonstrated that the best accuracy was achieved when the control points were evenly distributed throughout the control region. For the system under investigation, an accuracy of 1-2 mm in the x and y directions, 4-6 mm in the z direction and 6-7 mm for the resultant was obtained in a control space of 2.10 x 1.35 x 1.00 m. Additionally, the accuracy for points outside the control space and the systematic error associated with the control object were studied. Tests were done on a 32-point rectangular calibration frame, and the results indicated that the calibration errors could be reduced by 20-40% when an appropriate quadratic function was used to modify the standard DLT method.

Calibration↗
PubMed1996

On improving the accuracy of instrumented spatial linkage system.

Calibration is important for improving the accuracy of instrumented spatial linkage (ISL) in the application of biomechanical studies. The assumption of the linear performance of the potentiometer transducer has limited the improvement of the linkage accuracy. We present a non-linear numerical calibration procedure and double potentiometer design to improve the accuracy of ISL. Through the use of a three-degree-of-freedom linkage, the non-linear calibration procedure and the double potentiometer design were shown to be effective in reducing the ISL errors. The error, i.e. standard deviation for the angle decreased from +/-0.38 degree to +/-0.12 degree while the same for the translation decreased from +/-0.41 to +/-0.16 mm. A high-accuracy linkage system using low-cost potentiometers could be constructed by using our calibration method and double potentiometer design.

Calibration↗
PubMed1985

Relative observer accuracy for dichotomized variables.

We suggest that the relative accuracy of several observers of a disease manifestation can be assessed by comparing the strength of association between their observations and a known cause of that disease. In principle, the observer whose findings are most strongly associated with the causal variable has the least error. In practice many observations appear binary ("normal" or "abnormal") when the underlying distribution of the variable they measure is continuous. For this case of a dichotomized variable, several observers may find different prevalences of abnormality in the same sample either because their accuracy differs or because they use different thresholds above which they regard abnormality as present. A comparison of how strongly their observations are associated with a causal variable using statistical methods for binary observations may lead to incorrect conclusions about the relative accuracy of the observers. We suggest and evaluate a method, based on the biserial correlation coefficient, for comparing the relative accuracy of several observers who may differ in the thresholds they use.

Asbestosis↗
PubMed1987

Fine detail in body surface potential maps: accuracy of maps using a limited lead array and spatial and temporal data representation.

In order to evaluate the accuracy with which a limited lead array can be used to estimate fine details of the thoracic distribution of cardiac potentials, we compared 192-lead body surface maps and those constructed using a subset of 32 leads. We also evaluated preservation of detail in body surface maps reconstructed following spatial and temporal data representation, a method proposed for quantitative comparison of maps. Maps were analyzed with respect to four previously reported normal map features recorded with extensive lead arrays. The maps constructed from 32 leads accurately reproduced all map features with 92% or greater accuracy. Maps constructed after spatial and temporal data representation had a reproduction accuracy of 93% and 98% respectively for two map features more than 100 microV in amplitude but accuracy with respect to the two map features less than 100 microV in amplitude was 86% and 59% respectively. The study demonstrates that a selected limited lead array permits accurate estimation of the body surface distribution of cardiac potentials even when potentials are low level or occur in regions not directly sampled by a recording electrode. To represent potentials of less than 100 microV, more coefficients would be required to permit accurate spatial and temporal representation.

Electrocardiography↗
PubMed1990

Accuracy in clinical arrhythmia detection of a real-time Holter system (Oxford Medilog 4500).

The accuracy of a real-time analysis Holter system (Oxford Medilog 4500) in detecting ventricular and supraventricular arrhythmias was evaluated. Hand-counted data from randomly selected hours of 152 ECG monitorings of 152 patients were used as the control standard. Accuracy of the system was evaluated on 606 hours for premature ventricular complexes (PVC), PVC couplets and supraventricular extrasystoles (SVE), and on 1,789 hours for ventricular tachycardia (VT), accelerated idioventricular rhythm (AIVR), and supraventricular tachycardia (SVT). Sensitivity and positive predictive accuracy for the Oxford system were (1) 92.9% and 94.9% for PVC; (2) 90.1% and 87.8% for PVC couplets; (3) 98.1% and 56% for AIVR; (4) 80% and 82.3% for VT; (5) 88.6% and 56.5% for SVE, and (6) 43.7% and 60.2% for SVT. Furthermore, negative predictive accuracy, the ability to predict the total absence of an arrhythmic event in an hour, was determined. It was 91.7% for PVC, 99.5% for PVC couplets, 99.9% for AIVR, 99.7% for VT, 95% for SVE, and 98% for SVT. ventricular arrhythmias, whereas significant inaccuracies appear to exist in the analysis of supraventricular arrhythmias.

Algorithms↗
PubMed1980

Measurement accuracy of the mandibular kinesiograph--a computerized study.

Today's high-technology electronic and computer techniques have been applied to the long-standing problem of tracking mandibular movement and skeletal relation in research and diagnosis of mandibular function/dysfunction. The measurement established that within an area known as "clinical space" where most diagnostic data is derived, the linearity and quantitative accuracy ranged from error of 0 mm at intercuspation to 0.5 mm at worst error. This order of accuracy provides data that is qualitatively and quantitatively useful for research and diagnosis without the need for further correction. Computer processing further reduces the worst anywhere within the clinical space to 0.1 mm. Geometric skewing of the trace patterns that occur while taking data at mouth openings beyond clinical space (though not pronounced enough to affect the qualitative usefulness of the data) is readily corrected by computer processing. A microcomputer attached to the K5-R corrects the skew in real-time so that the data are displayed to an accuracy within 1.5% of exact values or a worst-case error less than 0.5 mm for a 30 mm vertical opening. When tested against a computer-controlled electronic measuring system, the accuracy and linearity parameters of the trace patterns confirmed the validity of the MKG recordings as precise representations of mandibular movement at the incisor point.

Computers↗
PubMed1982

The casting accuracy of nickel--chromium alloys for fixed prostheses.

The casting accuracy of four nickel--chromium alloys (Ultratek, Omega, Microbond N/P2, and Nobil-Ceram) was compared to that of a precious alloy, Jelenko "O". The experiment consisted of fabricating and fitting cast copings to a cobalt--chromium test preparation of a maxillary central incisor and measuring the marginal discrepancy in eight selected points. The experiment indicated that Jelenko "O" had the greatest casting accuracy, followed successively by Ultratek, Nobil-Ceram, Microbond N/P2, and Omega. Statistical analysis of the data revealed no significant difference between Jelenko "O" and Ultratek alloys in fit of five of eight test points, but Jelenko "O" was significantly better in fit than Nobil-Ceram, Microbond N/P2, and Omega alloys. The following conclusions may be drawn from this experiment: 1. The nickel--chromium alloys tested did not cast as consistently or as accurately as precious alloy Jelenko "O". 2. The casting accuracy may be related to the amount of casting shrinkage that occurs in each alloy type, and further research is necessary to determine if expansion compensation of the selected phosphate-bonded investment recommended by the alloy manufacturers is adequate for the casting shrinkage of the test alloys. 3. Alloy composition and technique parameters may also influence the accuracy of the casting, but further research is necessary to determine their singular effects.

Chemical Phenomena↗
PubMed1991

Predictive value: a model for dentists to evaluate the accuracy of diagnostic tests for temporomandibular disorders as applied to a TMJ scale.

The predictive value model for assessing the accuracy of diagnostic test results in the individual patient with a temporomandibular disorder is described. The use of predictive values to help the clinician ascertain the degree of confidence to be placed in diagnostic test results is illustrated. The predictive value model is used to study the accuracy of the TMJ Scale as a diagnostic tool. For all base rates between 0% and 100%, the predictive values of the TMJ Scale result in a gain in accuracy in confirming or excluding a diagnosis of a temporomandibular disorder. The TMJ Scale provides the dentist with improved accuracy of diagnostic decisions regarding the presence of temporomandibular disorders throughout the entire range of base rates found in clinical practice. Application of the predictive value model helps the dentist avoid serious diagnostic errors that could place both the patient and dentist at unnecessary risk.

Humans↗
PubMed1992

Accuracy of one-step versus two-step putty wash addition silicone impression technique.

This study compared the accuracy of one-step putty wash with two-step putty wash impression techniques. Five addition silicone impression materials-Mirror 3 (MR), Mirror 3 Extrude (ME), Express (E), Permagum (P), and Absolute(A)--were tested. A stainless steel model containing two full-crown abutment preparations was used as the positive control. Five replications for one-step and two-step putty wash impressions of the master model were made for each test material. Accuracy of the materials was assessed by measuring six dimensions on stone dies poured from impressions of the master model. Accuracy of addition silicone impression material is affected more by material than technique. Accuracy of the putty wash one-step impression technique was not different from the putty wash two-step impression technique except at one of the six dimensions where one-step was more accurate than two-step. Mirror 3 putty wash two-step impression presented less distortion than Mirror 3 Extrude putty wash one-step or two-step impression.

Analysis of Variance↗
PubMed1982

In vitro determination of accuracy of cardiac output measurements by thermal dilution.

The accuracy of cardiac output (C.O.) measurements by the thermodilution method was evaluated in an in vitro model within a flow range from 1 to 5 liters/min. For C.O. determinations, a 5F Swan-Ganz balloon-tipped thermodilution catheter and a 9520 Edwards computer were used. We made 420 measurements at known flow rates. In serial determinations, we achieved an overall accuracy of 86 to 93% compared to the reference flow; for single determinations, the accuracy ranged from 75 to 85%. The indicator volume (3, 5, or 10 cc) had no influence on the results. The thermodilution determinations at each flow rate were reproducible at between 2.5 and 8.5%. There was no difference in accuracy or reproducibility when ice-cold or room temperature saline was used. Caution in the interpretation of single C.O. determinations in low-flow states, i.e., in pediatric patients, is recommended.

Cardiac Catheterization↗
PubMed1996

Transesophageal dobutamine-atropine stress echocardiography: diagnostic accuracy for coronary stenosis detection and localization.

Transesophageal echocardiography with dobutamine-atropine stress (TE-DASE) is a recently described technique for evaluation of coronary artery disease (CAD). We undertook this study prospectively to determine the feasibility, reliability and safety of this procedure in patients with known CAD and to evaluate its diagnostic accuracy for coronary stenoses of varying severity. Thirty-seven patients who underwent coronary arteriography (CART) and TE-DASE within a 3-month interval without intervening ischemic events or revascularisation were included in the study CART and stress echograms were independently evaluated by different observers. Stenosis was measured with calipers and a > or = 50% lumen diameter stenosis was considered significant. A reduction or lack of endocardial motion and/or wall thickening on progressive incremental stress was considered an abnormal response. TE-DASE could be successfully completed in 33/37 (90%) patients. Using a modified 16-segment model of the left ventricle (LV), 15.2 +/- 0.8 segments/patient and 501/528 (95%) segments overall could be optimally evaluated. Inter-observer concordance for an abnormal response was 94%. Predictive accuracies for one-vessel disease (1-VD), two-vessel disease (2-VD) and three-vessel disease (3-VD) were 88, 58 and 23% respectively. Overall sensitivity for detection of a significant (> or = 50%) stenosis was 72% (32% for moderate (50-69%), 90% for severe (> or = 70%) stenosis) and specificity was 96%. Diagnostic accuracy for localisation of significant stenosis was 95% for the left anterior descending artery (LAD), 86% for the left circumflex artery (LCX) and 88% for the right coronary artery (RCA). There were no major complications. We conclude that TE-DASE is a safe, reliable and easily-performed procedure and provides excellent visualisation of myocardial segments. Diagnostic accuracy for detection of severe stenosis and its localisation is excellent.

Atropine↗
PubMed1991

Electrodermal differentiation of deception: perceived accuracy and perceived memorial content manipulations.

The demonstration of deception as a psychophysiological phenomenon requires a comparison of physiological responses to two conditions (experimental and control) which differ only with respect to deception. Such electrodermal (skin conductance response) differentiation was recently reported in the Differentiation of Deception paradigm, which controls for two potentially important sources of confounding in polygraph (often referred to as the Detection of Deception): differential question significance and differential frequency of question occurrence. The present study manipulated (between 32 subjects in a 2 x 2 design) two two-level, subjective factors in the paradigm: Perceived Accuracy of polygraphy (written and oral instructions characterising accuracy as high vs low) and Perceived Memorial Content (20 more complex, less personal, and less meaningful questions vs 6 less complex, more personal, and more meaningful questions). Significant differentiation of deception was again obtained, as was evidence for the effectiveness of the manipulations. However, the deception phenomenon was not clearly affected by either of the two subjective factors. In addition, one post-hoc test showed significantly increased differentiation under the low Perceived Accuracy condition, which is contrary to the widespread belief of polygraphers that high perceived accuracy is not only important but even essential for the detection of deception. However, the applied, polygraphic aim of detecting guilt in individuals is quite different from the scientific, psychophysiological aim of differentiating deception as a psychological process, and the phenomena involved probably have different causes.

Deception↗
PubMed1991

Accuracy of blood glucose estimates in adolescents with diabetes mellitus.

Although self-monitoring of blood glucose (SMBG) is an integral part of the daily self-care regimen for the effective management of insulin-dependent diabetes mellitus (IDDM), compliance with this task remains a significant problem, particularly for adolescents. Research should be focused on identifying other management approaches which may supplement SMBG. One potential approach involves placing greater reliance on the patient's own ability to estimate glucose levels. Although some research has examined blood glucose self-estimation in adults, little is known about this construct in children and adolescents. The purpose of the current study was to examine the accuracy of blood glucose self-estimates in adolescents with IDDM and examine the relation between child characteristics and accuracy. The results for 70 adolescents with IDDM indicated that as a group they were moderately accurate in estimating their glucose levels; however, much variability in accuracy was found among subjects. Subject characteristics were not found to be significantly related to accuracy.

Adolescent↗
PubMed1990

Accuracy in radiographic diagnosis: Dutch practitioners and dental caries.

The effective diagnostic accuracy of dentists is the missing link in models for calculating the optimal frequency for radiographic recall. The purpose of this study was to describe the accuracy of Dutch general dental practitioners using bitewing radiographs for the diagnosis and treatment of approximal caries in dentine. Practitioners from a 10 per cent (n = 444) national random sample were sent a set of simulated bitewings, a patient description and a diagnostic response form. The radiographs showed tooth surfaces with (n = 45) and without (n = 60) dentine caries. Microradiography of the sectioned teeth was used as a diagnostic reference standard. The participants were asked to diagnose dentine caries using a five-point certainty scale and decide if restorative treatment was indicated. The response was 62 per cent (n = 276). The area under a mean receiver operating characteristic curve for the practitioners was 88 per cent of the area representing optimal accuracy. Diagnostic accuracy, however, varied considerably between dentists. For caries considered to be 'probably' in the dentine mean sensitivity was 54 per cent (s.d. 14 per cent) and specificity was 97 per cent (s.d. 5 per cent). The pooled restorative treatment decisions of the dentists had a mean sensitivity of 62 per cent and a specificity of 96 per cent. More surfaces were considered in need of treatment than were diagnosed as 'probably' having dentine caries. Treatment decisions were more accurate than diagnostic ability might indicate. Paradoxically this may be because errors in visual ability were partly compensated for by 'over treatment' decisions.

Decision Making↗